Measure your source's voltage output ...

[dsavitsk]

I am looking for measurements of the voltage out level of various sources, commercial and otherwise.

Nominally, sources are "line level", but this turns out to be a term without a lot of real adherence. Consumer gear is said to be at -10dBV, which equates with ~0.316V RMS, but most sources seem to run hotter than that. Pro gear has a US standard (+4dBu or ~1.228V RMS which is 1.78dBV) and a German one (+6dBu, 1.55V RMS or 3.78dBV). Notice that V RMS, dBV, dBu, and dB are all different things -- you can convert between some of them at dB dBu dBFS dBV to volts conversion - calculator volt volts to dBu and dBV dB mW - convert dB volt convertor converter calculation online attenuation loss gain ratio reference audio engineering dBFS dBVU 0 dB audio logarithm level converter peak to p

So, in order to determine what level stuff actually outputs, it is pretty simple to just measure. To do that, you will need a 60Hz 0dB test tone, and a $5 multimeter. A test tone can be downloaded from Free download of bass test tones -- there are several available, but it is probably a good idea to standardize on one.

Basically, all you do is play the tone and measure the AC voltage on the meter. For balanced outputs, measure from pin 2 to 3. For single ended, from the pin to ground. You use a 60Hz tone because multimeters are designed to measure AC at the wall, which is 60Hz, so they tend to be reasonably accurate here. Some will work fine at other frequencies, but some probably won't.

To get the ball rolling, my WM8741 dac (http://www.head-case.org/forums/do-yourself/476-diy-amp-such-build-gallery-153.html#post331335) that takes the output directly from the chip is ~1.96V (balanced signal) or a little over 8dBu.

My other DACs run a little cooler -- for instance, my AD1865N-K based dac which uses a passive IV into C3g's that are parafeeded (parafed?) into Magnequest 15K:500 OPTs runs at ~1.32V, or ~4.6dBu.

Measurements of commercial cd players and dac's would be appreciated.

For extra credit, it would be interesting to measure the voltage out of listening level across headphones, but that might be another thread. It is best to do this with the phones attached.

Thanks!

[luvdunhill]

Doug:

I have just done this in fact, and used it to calibrate a LNMP. My source is 1.99 V balanced and 1.99 V single ended.

[dsavitsk]

My source is 1.99 V balanced and 1.99 V single ended.

What is the source?

[Duggeh]

If I do this, should I be using a test tone which matches the mains frequency over here, or 60hz also?

[dsavitsk]

I'd assume that meters will do fine with either 50 or 60Hz as I think they are pretty universal.

[cetoole]

My modded Adcom GDA600 measures 1.91V each channel.

[n_maher]

Might I suggest that it'd be a cool idea to compile (and directly enter) this information into a Google Spreadsheet? I'd suggest column headings of : Make/Model/Test Tone Freq/Meter Used/ACV as a start and have the sheet auto convert to dB.

[tkam]

also, if we get a good sized list going, might be worth turning this into an article here instead of just a forum thread.

[n_maher]

i'm guessing i shouldn't bother, since my source has a variable output?

Measuring it "wide open" would be the way to go if you do since IIRC any attenuation is done in the digital domain and not reflective of altering the output gain, just reducing the signal input at the output stage.

[dsavitsk]

attenuation is analog on the Cap II, not digital. the Cap I had the option of either. 100 step (maybe 99?) ladder.

Still probably best to measure it wide open as our interest here is what level the source can output.

Nate -- can you set up a spread sheet at the forum level to enter numbers into?

[n_maher]

Possible spreadsheet here - https://spreadsheets.google.com/ccc?key=0AqT3b5JN2i_fdG1XdTIwdWJub3dfbzltZDhnLWtfLVE&hl=en

Note, all users have full read/write access so be careful.

[The Monkey]

This is a nice idea. Wish I had done it for my previous DACs. I'll do it for the ones I currently have unpacked. It would also be interesting to compare to the manufacturer's published specs for the source.

[n_maher]

I'd like to request that anyone doing these measurements take them both with a 60Hz and 1kHz test tone.

Here's an easy source for tones - Free Test Tones Download -- Online Ear Training for Musicians and Sound Engineers - I took a look at the ones that Doug referenced and for whatever reason using a compressed file format seems somehow wrong to me. Feel free to point out why I'm an idiot.

[n_maher]

Bump, come on you slackers.

[guzziguy]

in the basement ...